1. Field of the Invention
This invention relates to medical articles and more particularly relates to a solventless method for lubricating articles.
2. Background of the Invention
Many occasions arise when it is necessary to puncture the skin with a metal device, generally of stainless steel, having a sharp point or edge. Representative of such devices are syringe needles, surgical blades, lancets, cannulas, catheter insertion devices and the like. In other cases, a cutting edge, such as a razor blade, is advanced across a skin surface.
When such a device is advanced across the skin or inserted through the skin, the skin is stretched and a certain amount of pain is experienced. It has been common practice for many years to lubricate the device to minimize pain.
Noncuring, nonpolar silicones, such as the DC.RTM.360 series of medical grade polydimethylsiloxanes (PDMS) available from Dow Corning Co. have been used. These products have the disadvantage of ease of wipe-away or migration from the surface to which they have been applied. Another problem with these lubricants is adhesion which develops over time when metal to plastic or two plastic surfaces are engaged by an interference fit. For plastic syringe barrels and associated plunger, Williams et al., in U.S. Pat. No. 4,767,414, discloses that plasma treatment of one of the surfaces and the oil overcomes adhesion. For a catheter-cannula assembly, Williamitis et al. discloses in U.S. Pat. No. 4,664,657 that adhesion can be mitigated if the PDMS is of high viscosity.
The problem of wipe-away is particularly severe when metal surfaces are lubricated with noncuring PDMS. For example, in the case of a hypodermic needle coated with PDMS, the coating may be substantially removed due to frictional wiping forces during penetration of the skin and vein, making subsequent removal of the needle difficult and painful to the patient. Migration during storage and inadvertent removal during processing is also a concern.
For these reasons, commercial syringe needles are usually coated with proprietary silicone-based lubricants applied by wiping, spraying or dip coating from solvents such as FREON.TM.. These lubricants reduce maximum penetration force by about 20% and usually contain silicone oil plus a room temperature vulcanizable silicone which serves as a matrix to prevent removal of lubricant during penetration. The matrix only minimizes the lubricant removal and penetration forces approach that of a dry needle after 2 to 3 sequential penetrations. Also, the standard commercial systems require long cure times on the order of one to several days. Exemplary of these lubricating systems is the disclosure in U.S. Pat. No. 3,574,673 to Schweiger of friction reducing coatings on blades consisting of alkylamine-modified methoxysiloxanes which undergo moisture curing at ambient temperature.
In similar fashion, U.S. Pat. No. 4,720,521 to Spielvogel discloses a noncuring lubricating PDMS occluded in a mixture of at least three curing silicones which adhere to a metal surface.
Copending application Ser. No. 628,139 of common assignee herewith discloses metal articles having a coating of a polar noncuring silicone lubricant.
Copending application Ser. No. 640,714 of common assignee herewith discloses a composition which includes an aqueous emulsion of a noncuring polar silicone lubricant and a metal article having a coating of the composition thereon.
U.S. Pat. No. 5,041,310 discloses a process for coating polymeric particles with an additive composition which includes a mobilizing oil, a radiation stabilizer and a gelling agent.
While the above disclosures all teach improved compositions and methods for lubrication, there remains a need for a composition and method which overcomes migration and wipe-away problems without a curing step using simple and inexpensive nonpolar silicones.